Transient display of a novel Fas ligand (FasL) protein chimeric with streptavidin (SA-FasL) on donor lymphocytes has been shown to effectively eliminate alloreactive T-effector cells (Teffs) after transplant, consequently preventing acute graft-versus-host disease (aGVHD), according to preclinical research findings published in Blood Advances.
“Our approach harbors significant potential as monotherapy or in combination with various clinical regimens to improve both the efficacy and safety of mismatched T-cell-replete hematopoietic cell transplants,” wrote Pradeep Shrestha, MD, of the University of Texas MD Anderson Cancer Center in Houston, and colleagues. The studied “approach may also improve donor lymphocyte infusion to manage relapse of hematologic malignancies following” hematopoietic cell transplantation, they added.
SA-FasL, existing as tetramers and oligomers, features strong apoptotic activity on Fas-expressing cells, according to researchers. Additionally, various transplantation models in previous research have shown SA-FasL can be positionally and temporarily displayed on both biotinylated biologic and nonbiologic surfaces with an in vivo half-life of approximately 3.5 days.
In the present study, researchers engineered spleen cells and human peripheral blood mononuclear cells (PBMCs) with SA-FasL, which was transiently displayed on the surface of biotinylated lymphocytes. Following activation in response to alloantigens in vitro and in vivo, both SA-FasL-engineered mouse and human T cells underwent apoptosis.
The investigators used a haploidentical myeloablative transplant model to evaluate whether the engineering of donor T cells would prevent aGVHD. First, the investigators transplanted C57BL/6 splenocytes (2×107) engineered with various doses of SA-FasL protein with whole bone marrow cells (1×107) into lethally irradiated F1 recipients.
The recipients of nonengineered splenocytes or splenocytes with SA protein demonstrated high-grade clinical GVHD scores, as well as considerable weight loss. In contrast, more than 70% of mice that were transplanted with SA-FasL-engineered splenocytes at doses greater than 10 ng/106 cells survived (p<0.0001) and had improvements in clinical aGVHD scores and weight.
Mice that survived more than 100 days demonstrated full donor chimerism in peripheral blood, bone marrow, and spleen. Additionally, these mice demonstrated efficient reconstitution of Treg (CD4+CD25+FoxP3+), Teff (CD4+CD44hiCD62L-), and natural killer (NK1.1+CD3-) cells. Furthermore, these long-term survivors were deemed immunocompetent given that they accepted BALB/c (H-2d) skin grafts while rejecting C3H (H-2k) third-party grafts within a 24-day period.
Compared with recipients of nonengineered splenocytes, the liver and the small and large intestines of mice transplanted with SA-FasL-engineered splenocytes showed reduced levels of transcripts for interleukin (IL) 1β, IL-6, tumor necrosis factor alpha, interferon gamma, and IL-23 proinflammatory cytokines on day seven after transplant.
On day 21, the researchers observed significant reductions in transcripts for CCL2 in the liver (p<0.01) and small intestine (p<0.05) of SA-FasL-engineered splenocytes, which the investigators wrote was “consistent with the role of this chemokine in the recruitment of CD8+ Teff cells into target tissues for GVHD.”
Transcripts for granulocyte-macrophage colony-stimulating factor, which the researchers explained are involved in aGVHD pathology, were also significantly reduced in the liver of SA-FasL-engineered splenocytes compared with the nonengineered splenocytes at day seven (p<0.001). In addition, the SA-FasL-engineered splenocytes demonstrated reduced T-bet transcription factor expression in all GVHD target organs.
In a xenogeneic setting, the transient display of SA-FasL on human PBMCs also showed efficacy in preventing aGVHD. More specifically, mice that received SA-FasL-engineered PBMCs had improvements in survival, significant reductions in clinical GVHD scores, and maintenance of body weight. Because survival improvements were found to be dose dependent, the researchers suggested additional investigation is needed to determine whether “higher concentrations of SA-FasL result in further improved efficacy in abrogating aGVHD in this pre-clinical model of the human disease.”
Any conflicts of interest declared by the authors can be found in the original article.
Shrestha P, Turan A, Batra L, et al. Engineering donor lymphocytes with Fas ligand protein effectively prevents acute graft-versus-host disease [published online, 2023 Feb 13]. Blood Adv. doi: 10.1182/bloodadvances.2022008495.